Thermochemistry of the Ir + SO reaction using guided ion beam tandem mass spectrometry and theory.

Kinetic energy dependences of the reactions of Ir (F) with SO were studied using a guided ion beam tandem mass spectrometer and theory. The observed cationic products are IrO, IrS, and IrSO, formed in endothermic reactions. Bond dissociation energies (BDEs) of the products are determined by modeling the kinetic energy dependent product cross sections: D(Ir-O) = 4.27 ± 0.11 eV, D(Ir-S) = 4.03 ± 0.06 eV, and D(Ir-SO) ≥ 2.95 ± 0.06 eV. The oxide BDE agrees well with literature values, whereas the two latter results are novel measurements. Quantum mechanical calculations are performed at the B3LYP level of theory using the def2-TZVPPD basis set for all product BDEs with additional calculations for IrS, IrO , and IrSO at the coupled cluster with single, double, and perturbative triple excitation levels with def2-QZVPPD and aug-cc-pVXZ (X = T and Q and for IrS, also X = 5) basis sets and complete basis set extrapolations. These theoretical BDEs agree reasonably well with the experimental values. A (IrO ), Δ (IrS), and A″/A' (IrSO) are found to be the ground states after including empirical spin-orbit corrections. The potential energy surfaces including intermediates and transition states for each reaction are also calculated at the B3LYP/def2-TZVPPD level. The formation of MO (M = Re, Os, and Ir) from M + SO reactions is compared with those from the M + O and M + CO reactions, where interesting trends in cross sections are observed. Overall, these studies suggest that the M + O reactions had restrictions associated with reactions along A' and A″ surfaces.